Bar-J Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bar-J Ranch clear sky chart from 2005-11-06 to 2024-02-10.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	4 5% 2 4 4 3 4 5% 6% 8% 55%	78400
	Night	3 5% 2 4 4 2 3 4 5% 7% 60%	80625
Transparency	Day	24% 6% 12% 25% 24% 9%	78113
	Night	22% 6% 13% 27% 25% 8%	80435
Seeing	Day	10% 16% 34% 26% 12% 2	14397
	Night	6% 10% 37% 34% 12% 1	24605

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	4 2 4 3 2 4 4 5% 8% 63%	2538
	11th to 20th	Day	1 2 3 5% 4 3 4 5% 5% 9% 60%	2764
	21st to end	Day	1 7% 4 6% 4 2 3 3 5% 7% 57%	3146
February	1st to 10th	Day	1 6% 3 6% 3 1 3 3 4 8% 63%	1701
	11th to 20th	Day	1 3 2 3 3 2 2 4 6% 9% 64%	1727
	21st to end	Day	5% 3 5% 3 2 3 4 5% 7% 61%	1480
March	1st to 10th	Day	1 4 2 4 4 2 4 3 4 9% 61%	1815
	11th to 20th	Day	4 6% 2 5% 5% 3 4 5% 5% 8% 53%	1980
	21st to end	Day	3 7% 3 5% 4 3 5% 5% 6% 9% 51%	2286
April	1st to 10th	Day	3 5% 3 4 5% 3 4 4 5% 9% 55%	2160
	11th to 20th	Day	6% 9% 4 6% 4 3 4 5% 5% 7% 48%	2131
	21st to end	Day	7% 8% 3 5% 4 4 5% 6% 6% 6% 47%	2160
May	1st to 10th	Day	7% 7% 3 5% 4 3 6% 7% 7% 8% 44%	2200
	11th to 20th	Day	8% 7% 3 5% 5% 4 5% 6% 7% 9% 40%	2455
	21st to end	Day	6% 6% 2 4 4 3 5% 6% 6% 8% 49%	2724
June	1st to 10th	Day	4 4 1 4 5% 3 6% 6% 8% 9% 49%	2520
	11th to 20th	Day	5% 4 1 3 4 3 5% 5% 6% 8% 56%	2520
	21st to end	Day	4 4 2 4 5% 3 6% 6% 7% 9% 50%	2520
July	1st to 10th	Day	7% 4 2 4 6% 3 5% 6% 7% 9% 47%	2520
	11th to 20th	Day	6% 3 1 5% 4 4 6% 6% 7% 9% 47%	2520
	21st to end	Day	6% 7% 3 6% 6% 5% 8% 7% 8% 9% 35%	2596
August	1st to 10th	Day	7% 5% 3 6% 7% 5% 6% 6% 7% 9% 39%	2324
	11th to 20th	Day	6% 4 2 4 5% 3 6% 6% 7% 9% 48%	2123
	21st to end	Day	6% 5% 3 5% 4 3 4 6% 7% 8% 49%	2376
September	1st to 10th	Day	6% 5% 2 5% 4 3 4 5% 6% 7% 54%	2160
	11th to 20th	Day	5% 4 2 4 3 3 3 5% 6% 7% 59%	2159
	21st to end	Day	6% 3 1 2 3 2 3 3 4 5% 66%	1967
October	1st to 10th	Day	5% 4 1 4 4 2 4 4 5% 8% 59%	1800
	11th to 20th	Day	3 3 1 3 2 2 3 3 3 5% 72%	1800
	21st to end	Day	4 6% 1 3 3 1 3 3 4 5% 66%	1971
November	1st to 10th	Day	1 2 1 3 2 1 2 2 4 7% 73%	1673
	11th to 20th	Day	1 2 2 3 3 2 2 2 3 7% 73%	1710
	21st to end	Day	1 4 2 3 4 2 3 3 3 9% 66%	1634
December	1st to 10th	Day	5% 2 4 3 1 2 4 5% 8% 66%	1520
	11th to 20th	Day	2 3 2 3 3 1 3 4 6% 10% 63%	1926
	21st to end	Day	1 4 2 5% 4 2 3 4 5% 8% 62%	2794
January	1st to 10th	Night	5% 3 6% 4 2 4 4 4 8% 59%	4417
	11th to 20th	Night	1 2 1 3 3 2 3 4 5% 8% 67%	4234
	21st to end	Night	1 6% 2 4 4 2 3 4 4 6% 63%	4521
February	1st to 10th	Night	1 5% 2 5% 3 2 2 3 3 8% 66%	2463
	11th to 20th	Night	1 4 3 5% 4 2 3 4 4 7% 62%	2118
	21st to end	Night	1 6% 3 5% 3 2 3 4 4 6% 65%	1776
March	1st to 10th	Night	1 4 2 4 4 2 2 3 6% 7% 65%	2142
	11th to 20th	Night	3 6% 2 4 4 2 4 4 6% 8% 58%	1980
	21st to end	Night	2 6% 3 4 3 2 4 3 4 7% 61%	2068
April	1st to 10th	Night	3 6% 3 4 3 1 3 3 4 7% 63%	1800
	11th to 20th	Night	7% 9% 3 4 3 2 4 3 4 6% 56%	1777
	21st to end	Night	7% 7% 2 4 3 2 3 3 5% 7% 56%	1800
May	1st to 10th	Night	9% 8% 3 4 3 3 3 4 5% 6% 52%	1757
	11th to 20th	Night	10% 9% 3 5% 4 2 3 5% 6% 7% 45%	1436
	21st to end	Night	10% 5% 2 3 3 2 4 4 5% 8% 54%	1552
June	1st to 10th	Night	6% 3 2 2 3 2 4 4 6% 11% 58%	1440
	11th to 20th	Night	4 3 1 3 2 2 3 4 6% 8% 65%	1440
	21st to end	Night	5% 3 1 3 4 2 4 5% 7% 9% 55%	1440
July	1st to 10th	Night	9% 4 2 5% 6% 4 5% 6% 7% 8% 45%	1440
	11th to 20th	Night	5% 4 2 3 4 2 5% 5% 6% 11% 54%	1440
	21st to end	Night	6% 5% 2 6% 6% 4 6% 7% 9% 11% 37%	1718
August	1st to 10th	Night	7% 4 2 5% 6% 4 6% 6% 8% 9% 44%	1614
	11th to 20th	Night	7% 4 2 4 4 3 4 6% 8% 8% 49%	1778
	21st to end	Night	6% 4 2 4 4 4 5% 5% 6% 10% 50%	1980
September	1st to 10th	Night	7% 5% 2 5% 5% 3 4 4 7% 9% 49%	1800
	11th to 20th	Night	8% 4 1 3 3 2 3 3 5% 8% 61%	1800
	21st to end	Night	6% 5% 2 3 3 2 3 4 4 5% 64%	1988
October	1st to 10th	Night	6% 5% 2 3 3 2 3 4 5% 6% 62%	2160
	11th to 20th	Night	2 2 1 2 2 1 3 3 3 5% 75%	2160
	21st to end	Night	5% 5% 2 3 2 1 3 3 5% 5% 66%	2376
November	1st to 10th	Night	1 2 1 3 2 1 2 2 4 7% 73%	2395
	11th to 20th	Night	3 2 3 3 2 3 3 3 5% 74%	2470
	21st to end	Night	2 6% 2 3 2 2 3 3 4 7% 67%	2541
December	1st to 10th	Night	3 2 4 4 2 3 3 5% 6% 68%	2660
	11th to 20th	Night	1 4 2 4 3 2 3 4 6% 9% 62%	3271
	21st to end	Night	1 5% 2 4 4 2 3 4 5% 7% 61%	4873

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 7% 11% 34% 26% 6%	2539
	11th to 20th	Day	18% 7% 11% 30% 30% 4	2764
	21st to end	Day	24% 4 11% 34% 23% 4	3146
February	1st to 10th	Day	20% 6% 11% 31% 22% 9%	1701
	11th to 20th	Day	18% 5% 10% 30% 31% 7%	1737
	21st to end	Day	22% 4 9% 25% 27% 13%	1480
March	1st to 10th	Day	20% 5% 9% 28% 30% 9%	1815
	11th to 20th	Day	26% 5% 10% 28% 26% 5%	1980
	21st to end	Day	26% 7% 10% 29% 21% 7%	2286
April	1st to 10th	Day	25% 6% 11% 24% 23% 12%	2160
	11th to 20th	Day	32% 6% 7% 26% 20% 9%	2134
	21st to end	Day	31% 8% 10% 24% 21% 6%	2160
May	1st to 10th	Day	32% 8% 12% 24% 19% 5%	2200
	11th to 20th	Day	36% 8% 18% 20% 13% 4	2459
	21st to end	Day	29% 8% 13% 21% 20% 10%	2724
June	1st to 10th	Day	26% 8% 16% 20% 20% 10%	2520
	11th to 20th	Day	22% 6% 10% 19% 24% 20%	2520
	21st to end	Day	25% 7% 12% 21% 23% 12%	2520
July	1st to 10th	Day	31% 8% 13% 17% 21% 11%	2451
	11th to 20th	Day	28% 8% 14% 27% 17% 7%	2445
	21st to end	Day	38% 10% 20% 18% 11% 2	2452
August	1st to 10th	Day	36% 11% 15% 16% 15% 7%	2309
	11th to 20th	Day	28% 8% 13% 21% 21% 10%	2123
	21st to end	Day	28% 6% 14% 23% 22% 7%	2376
September	1st to 10th	Day	26% 5% 11% 20% 23% 14%	2160
	11th to 20th	Day	21% 5% 11% 21% 26% 15%	2159
	21st to end	Day	20% 4 7% 23% 34% 12%	1967
October	1st to 10th	Day	22% 5% 11% 22% 29% 12%	1800
	11th to 20th	Day	15% 3 7% 22% 35% 18%	1800
	21st to end	Day	20% 3 6% 28% 30% 13%	1971
November	1st to 10th	Day	12% 3 10% 23% 38% 14%	1673
	11th to 20th	Day	14% 4 6% 35% 33% 9%	1710
	21st to end	Day	18% 4 7% 28% 31% 12%	1634
December	1st to 10th	Day	16% 5% 15% 30% 25% 8%	1520
	11th to 20th	Day	16% 4 13% 29% 31% 6%	1924
	21st to end	Day	18% 6% 11% 27% 28% 10%	2794
January	1st to 10th	Night	23% 5% 10% 32% 27% 3	4417
	11th to 20th	Night	14% 6% 11% 34% 28% 5%	4234
	21st to end	Night	23% 5% 15% 34% 19% 4	4521
February	1st to 10th	Night	20% 4 12% 34% 23% 7%	2463
	11th to 20th	Night	23% 5% 11% 29% 27% 5%	2118
	21st to end	Night	21% 3 7% 28% 30% 10%	1776
March	1st to 10th	Night	17% 5% 11% 28% 31% 8%	2142
	11th to 20th	Night	22% 6% 12% 31% 24% 4	1980
	21st to end	Night	23% 6% 10% 30% 28% 3	2068
April	1st to 10th	Night	21% 6% 12% 26% 27% 9%	1800
	11th to 20th	Night	29% 4 10% 28% 20% 9%	1777
	21st to end	Night	28% 5% 14% 27% 19% 6%	1800
May	1st to 10th	Night	31% 5% 12% 26% 19% 6%	1757
	11th to 20th	Night	37% 8% 17% 18% 15% 5%	1437
	21st to end	Night	26% 8% 17% 20% 18% 10%	1552
June	1st to 10th	Night	21% 7% 20% 24% 16% 13%	1440
	11th to 20th	Night	17% 5% 12% 22% 23% 21%	1440
	21st to end	Night	23% 7% 14% 22% 19% 14%	1440
July	1st to 10th	Night	33% 10% 13% 20% 15% 8%	1400
	11th to 20th	Night	22% 8% 20% 29% 14% 7%	1392
	21st to end	Night	35% 13% 26% 17% 7% 1	1623
August	1st to 10th	Night	32% 14% 19% 17% 11% 7%	1605
	11th to 20th	Night	28% 9% 18% 25% 15% 5%	1778
	21st to end	Night	27% 9% 15% 28% 16% 5%	1980
September	1st to 10th	Night	29% 8% 12% 22% 19% 10%	1800
	11th to 20th	Night	22% 5% 13% 22% 24% 14%	1800
	21st to end	Night	21% 4 10% 25% 31% 9%	1988
October	1st to 10th	Night	23% 6% 13% 22% 25% 12%	2160
	11th to 20th	Night	13% 3 7% 22% 39% 16%	2160
	21st to end	Night	20% 4 8% 28% 29% 11%	2376
November	1st to 10th	Night	12% 3 11% 30% 33% 11%	2395
	11th to 20th	Night	15% 3 8% 34% 32% 9%	2470
	21st to end	Night	18% 3 10% 26% 33% 9%	2541
December	1st to 10th	Night	18% 5% 14% 31% 26% 7%	2660
	11th to 20th	Night	18% 6% 13% 29% 31% 4	3272
	21st to end	Night	20% 7% 14% 25% 28% 6%	4873

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 18% 39% 24% 10%	270
	11th to 20th	Day	11% 18% 44% 26% 1 1	270
	21st to end	Day	3 16% 47% 26% 7% 1	297
February	1st to 10th	Day	10% 25% 45% 17% 1 1	267
	11th to 20th	Day	9% 25% 47% 14% 4 1	240
	21st to end	Day	13% 25% 44% 15% 3	198
March	1st to 10th	Day	10% 25% 40% 21% 3	255
	11th to 20th	Day	15% 24% 39% 18% 4	420
	21st to end	Day	17% 33% 38% 11% 2	462
April	1st to 10th	Day	16% 32% 32% 15% 4	420
	11th to 20th	Day	24% 29% 33% 12% 2	412
	21st to end	Day	17% 32% 30% 16% 4	420
May	1st to 10th	Day	14% 26% 34% 18% 7% 1	463
	11th to 20th	Day	12% 17% 32% 26% 10% 2	625
	21st to end	Day	12% 16% 30% 28% 14%	679
June	1st to 10th	Day	7% 12% 32% 31% 15% 4	630
	11th to 20th	Day	6% 13% 37% 30% 12% 3	630
	21st to end	Day	5% 14% 31% 30% 18% 3	630
July	1st to 10th	Day	7% 6% 24% 33% 27% 4	621
	11th to 20th	Day	6% 3 22% 35% 29% 5%	618
	21st to end	Day	8% 5% 19% 38% 25% 5%	538
August	1st to 10th	Day	11% 6% 26% 38% 15% 4	447
	11th to 20th	Day	6% 8% 32% 31% 19% 4	437
	21st to end	Day	9% 6% 30% 34% 18% 3	495
September	1st to 10th	Day	7% 10% 30% 32% 18% 3	450
	11th to 20th	Day	6% 10% 40% 30% 12% 2	449
	21st to end	Day	9% 11% 23% 33% 20% 3	270
October	1st to 10th	Day	9% 14% 27% 25% 21% 3	270
	11th to 20th	Day	9% 18% 30% 27% 16% 1	270
	21st to end	Day	12% 18% 32% 25% 12% 1	297
November	1st to 10th	Day	8% 17% 39% 24% 12% 1	270
	11th to 20th	Day	9% 14% 41% 26% 7% 2	270
	21st to end	Day	9% 14% 46% 24% 7%	270
December	1st to 10th	Day	10% 19% 43% 21% 6%	270
	11th to 20th	Day	7% 19% 51% 17% 7%	270
	21st to end	Day	12% 24% 41% 17% 5% 1	297
January	1st to 10th	Night	4 15% 45% 28% 6% 1	950
	11th to 20th	Night	4 16% 50% 24% 6%	832
	21st to end	Night	2 11% 52% 30% 5%	836
February	1st to 10th	Night	4 12% 59% 23% 2	758
	11th to 20th	Night	5% 15% 53% 24% 4	704
	21st to end	Night	3 17% 57% 22% 1	592
March	1st to 10th	Night	3 16% 48% 28% 4	720
	11th to 20th	Night	6% 11% 42% 34% 7%	720
	21st to end	Night	6% 14% 48% 29% 4	682
April	1st to 10th	Night	7% 16% 42% 32% 3	540
	11th to 20th	Night	12% 15% 36% 31% 6%	533
	21st to end	Night	11% 12% 36% 34% 6%	540
May	1st to 10th	Night	12% 11% 31% 38% 8% 1	540
	11th to 20th	Night	12% 8% 27% 39% 13% 1	531
	21st to end	Night	12% 7% 30% 36% 15%	584
June	1st to 10th	Night	7% 5% 24% 44% 19% 2	540
	11th to 20th	Night	4 5% 28% 49% 14% 1	540
	21st to end	Night	5% 3 19% 47% 26% 1	540
July	1st to 10th	Night	8% 3 11% 42% 32% 3	525
	11th to 20th	Night	5% 1 10% 44% 36% 3	522
	21st to end	Night	7% 2 7% 39% 43% 2	591
August	1st to 10th	Night	9% 3 11% 40% 35% 2	537
	11th to 20th	Night	7% 1 12% 50% 27% 2	534
	21st to end	Night	6% 2 13% 46% 31% 2	594
September	1st to 10th	Night	7% 2 15% 47% 25% 3	540
	11th to 20th	Night	9% 2 19% 47% 21% 1	540
	21st to end	Night	7% 6% 23% 46% 17% 1	548
October	1st to 10th	Night	8% 5% 34% 39% 13% 1	720
	11th to 20th	Night	3 5% 39% 39% 13%	720
	21st to end	Night	7% 8% 39% 35% 11% 1	792
November	1st to 10th	Night	3 11% 44% 33% 8%	915
	11th to 20th	Night	4 15% 45% 29% 7%	950
	21st to end	Night	5% 12% 44% 35% 4	950
December	1st to 10th	Night	3 14% 49% 30% 4	950
	11th to 20th	Night	3 13% 55% 24% 5%	950
	21st to end	Night	5% 18% 51% 23% 3	1045

Page generated at 2024-02-07 04:11:54. Version ac07

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